Butylated hydroxytoluene, also known as BHT, with the European food additive number E321. This ingredient is a synthetic phenolic compound that can be used as an antioxidant, preservative and stabilizer in fats and oils. It is added to preserve freshness and prevent spoilage mainly for cereals, shortenings, potato chips, margarines and nuts.
Commercial BHT is produced by reacting 4-methylphenol (p-cresol) with isobutylene (2-methylpropene) with a catalyst. (1).
4-methylphenol is obtained from the sulfonation of toluene (derived from the distillation of petroleum) and afterward heated with sodium hydroxide. 2-methylpropene is also made from petroleum.
|Appearance||White crystalline powder or flake, odorless or with a characteristic faint aromatic odor|
|Other names||Butylhydroxytoluene, 2,6-ditertiary-butyl-p-cresol, 4-methyl-2,6-ditertiarybutylphenol|
|Solubility||Insoluble in water, freely soluble in food fats and oils|
BHT, BHA and TBHQ are the synthetic phenolic antioxidants commonly added/mixed together to delay or prevent the rancidity of fats and oils, and the loss of activity of fat-soluble vitamins in foods and cosmetics.
BHA and BHT are often used with other chemicals to perform a synergistic antioxidant activity, such as with ascorbic acid, citric acid, or phosphoric acid.
The following processed food may contain BHT:
- Edible fats
- Fried foods
- Breakfast cereals
- Instant noodles, rices
Two types food antioxidants
Food antioxidants are basically classified into two types:
1. Water soluble antioxidants
2. Fat soluble antioxidants
Fat soluble antioxidants commonly refer to natural or synthetic phenolic antioxidants, which used for freshness by delaying or preventing the oxidation of unsaturated fatty acids in oils & fats.
Edible oils and fats are susceptible to be oxidized to rancidity if exposed to light, heat, enzymes, or metal ions, especially for vegetable oils rich in unsaturated fatty acids. Therefore, it is necessary to add antioxidants in order to maintain the original properties and nutritional values, improve the stability and prolong the shelf life.
Vegetable oils need the use of antioxidants to preserve freshness; meanwhile, animal fats are short of natural antioxidants and also need antioxidants to keep solid stable.
Corn is the primary grain used in the feed industry, but its quality and nutrition would be influenced during the shelf life mainly due to the high content of unsaturated fatty acids in the corn embryo, which is prone to oxidative rancidity. BHT can be used to prevent oxidative deterioration in corn by removing free radicals.
BHT is used as an antioxidant and masking agent (2) in cosmetics and personal care products.
The common cosmetics and personal care products with BHT:
- Skin care products
- Hair oil
- Body wash
The plastic packaging (e.g. polyethylene and polypropylene films) of food and cosmetics also use food grade BHT as an antioxidant to prevent aging.
The non-desirable chemicals, such as aldehydes, ketones, and acids are produced during the oxidation process of oils and fats, which not only affect the flavor and color of oils and fat-containing foods, but also lower quality and shorten the shelf life, or even bring dangers to the health of consumers.
Phenolic antioxidants share the same antioxidative mechanism. BHT acts as an inhibitor of free radical-mediated processes and prevents the oxidative rancidity of oils and fats by providing hydrogen ions to scavenge free radicals, and finally interrupt the chain reaction of the oxidation process.
Yes, the safety has been approved by the authorized parties, e.g. FDA, EFSA and JECFA. However, consumers are afraid there may be possible side effects at high doses and maybe it is this reason that General Mills removed BHT in many of its cereals in 2015 (3) .Vitamin E can be an alternative if people want to replace it.
BHT is generally regarded as safe (GRAS) (4) and used as an antioxidant alone or in combination with BHA with the maximum use level from 0.001% to 0.02% in dry breakfast cereals, as an emulsion stabilizer for shortenings and processed potato products (e.g. flakes, granules, shreds). (5)
Butylated Hydroxytoluene (E321) is listed in Commission Regulation (EU) No 231/2012 as an authorised food additive and categorized in “ additives other than colours and sweeteners” (6).
Safety re-evaluation in 2012
EFSA concluded that BHT was not genotoxicity but cancer may be caused at high dosage in some animals. An ADI of 0.25 mg/kg bw/day was established in 2012. (7)
Its application is listed together with BHA and propyl gallate, with the maximum level “25-400mg/kg”. The following are some of its uses (8):
- Fats and oils for heat-treated foods
- Frying oil, frying fat and fat from lard, fish oil, beef, poultry and sheep
- Chewing gum
- Seasonings and condiments
- Solid/liquid form of food supplements (not for infants and young children)
UK Food Standards Agency
Categorized in “Antioxidants” (9)
Food Standards Australia New Zealand
It is an approved ingredient in Australia and New Zealand with the code number 321. (10)
Function Class: food additives, antioxidants. (11)
Acceptable daily intake: ADI “0-0.3 mg/kg bw” set in 1995. (12)
Is BHT vegan?
Yes, it is vegan as the raw materials – 4-methylphenol and isobutylene are all derived from petroleum; and the animal-derived products are not used in the manufacturing process of BHT, so it is suitable to the diet of vegetarians.
Does BHT cause cancer?
As the evidence of carcinogenicity is inadequate in humans and inadequate or limited in experimental animals, BHT is classified in “Group 3” as “Not classifiable as to its carcinogenicity to humans” by the International Agency for Research on Cancer (IARC). (13)
BHT vs BHA vs TBHQ vs PG
Compared with other phenolic antioxidants, BHT doesn’t react with metal ions to generate color, nor does it have the peculiar smell of BHA, and the price is much lower than BHA.
Its antioxidative performance is similar with that of BHA, but less effective than TBHQ and PG, mainly due to the number of hydroxyl groups, substitution groups, and substitution positions in the structure.
Now you may have a knowledge of the preservative & antioxidant – butylated hydroxytoluene (E321), from the following aspects:
- Manufacturing processes
- Purposes in food, feed, cosmetics and packaging
- Two types of food antioxidants: water soluble and fat soluble antioxidants
- Approved safety
- Possible side effects
- FAQs: is it vegan, a carcinogen, and comparison with BHA, PG and TBHQ
What kinds of food labels have you found this ingredient in, feel free to let me know in the comments.